Ettoke -bellini



Jan. 15, 1929.

E. BELLINI BALAncm 'nmxoeomomsrsa Filed March 19, 1926 INVENTOR ETTOREBELHNI BY A TORNEY Patented Jan. 15, 1929.

ETTOBEBELLINI, or ra ars) FRANCE.

BALANCING aAnroeonIoMn'rEia.

Application filed March19, weasel-m1 No. 95,824, m in France May 8,1925.

It is well known that symmetry in -coils or loops used in. connectionwith radiogoniometry work is of great importance. The slightestdeficiency insymmetry produces wrong minimum signal strengths inreception, and this leads to more or less great errors in the taking ofbearings. r

' French Patent No. 567,587 discloses means adapted to insure almostexact symmetry, the

scheme'in question being here-produced in.

Fig. 1. To be true, symmetry is'not absolutely exact, since one of thecoats of'the variable condenser is connected with the grid of the firstthermionic tube. Since theheating battery is grounded and also themiddle point of the coil, it follows that the resistances and thecapacitance between grid and filament are governed by the middle pointof the coil and one armature of the condenser, and this, as will beunderstooch'makes the coil or loop dissymmetric, strictly speaking. InFig. 1 the said capacity and resistance are indicated by dotted lines.Now, the capacitance is usually of anorder of several centimeters, whilethe resistance is very high. In most cases, the symmetry of the loopwill be practically perfect. But conditions change, if very strongsignals are received, or if the amplifier starts oscillating for'somereason.

or another. Indeed, in all of such cases the filament-grid resistancebecomes relatively low; and since the loop is then appreciablydissymmetrical, it follows that the minimum values of the incomingsignal vanish, and

this makes the taking of bearings diificult if not entirely impossible.

The present invention will be readily apparent when read in connectionwith the accompanying drawing in which:

Fig. 1 is'a diagrammatic view of a loop andits associated tube. 7

Figs. 2, 3 and 4 are modifications of the method of balancing the loop.

Now, according to the invention forming the object to this inventionthis inconvenience and defect is obviated by connecting the other coatof the variable condenser with a tube similar to the other, as shown inFig. 2. This auxiliary tube, which serves solely for the purpose ofrestoring balanced conditions, can be called the balancing tube. Theplate of the latter may be united with the positive pole of the platebattery either directly or else through the intermediary of aresistance,

a self-inductance coil, or the primary of a radio-frequency transformeridentical to g f 1, 98,332 I those inserted inthe plate circuit ofthefirst.

amplifier-tube. The secondary-cirouit of this transformer may beleftopen, or else may be connectedinseri'es or in parallel with thesecondary of the rf. transformer of-thefir'st amplifier tube.

bodiments of this idea selected from agreat numberof'possibl'e schemesare 'illustrated'in Figs?) and 4. According to Fig. 3, a coilA;

isdisposed across the terminals of condenser; B pertainlng to the loopC; a coilDarranged in series in the plate circuit of thecompe'nsatlngtube E may be coupled. magnetically The equipment further includespreferably a connect-ion with ground through a variable resistanceFofthe middle point of coil 0, I and further a ground connectionof theheatr 1 with the coil A thereby introducing reaction. 7

ing battery G jointly serving the tubeE and the amplifier arrangement inwhich tube H 1 constitutes the first element.

Fig. 4: l represents an. installation comprising the samearrangements,'and which differs from the precedingscheme only bythedivision into two parts A and A1, of coil A shownin-Fig.*3, and theinsertionof each of said. parts in series in ,the'loop upon either sideof the condenser. Y

This method to obtain reaction or to receive by the autodyne methodoffers great advan tages especially in the caseofwork withshort waves,where a lack of symmetry in the loop, even when of but small value,causes immediatelya loss of the minimum signal point and thus preventsthe production of an even tenna having a tuning condenser connectedtherewith, a groud connection symmetrical V with respect to saidcondenser having a re-- sistance in series therewith, and electrondischarge apparatus having two pairs of gridcathode and anodecathodecircuits grounded at the cathode terminals, said grids being connectedrespectively to opposite plates of the condenser. g r

2. In directional aerial systems, a loopantenna having a tuningcondenser connected charge apparatus having two pairs of gridcathode andanode-cathode circuits ground ed at" the cathode terminals, said gridsbeing connected respectively to opposite plates of the condenser, aninductance symmetrically connected with said condenser, a secondinductance In one of the anode-cathode circu its ininductive relation tothe first inductance,

the otherof said anode cathode circuits belIlgflCltlPtQCl to beassociated with indicating apparatus.

8. In directional aerial systems, a loop antenna having atuningcondenser connected therewith, aground connection symmetrical withrespect to said condenser havinga variable resistance in seriestherewith, and elec tron dischargeapparatus having two pairsofigrid-cathode and anode-cathode circuits grounded at the cathodeterminals, said grids being connected respectively to opposite plates ofthe condenser, apair of inductances electrodes, grounded heatlng meansfor said symmetrically connected in series with said condenser, a thirdinductance" in one: ofthe anode-cathode circuits in inductive relationto'said pair or" inductances, the other of said anode cathode circuitsadapted to be associat'ediwith indicating apparatus.

4:. In theart of radio signalling, means for electrically balancing aradiogoniometer coil having .a tuning condenser connected therewith,comprising an' electron' discharge tube connected with each of theopposite plates of said condenser, atuning coil 7 associated with saidcondenser, and acoupling-coilin the plate circuit of one of saidelectron discharge tubes variably coupled to saicllast mentioned coil; r7

5. In the artof radio signalling, means for electrically balancing aradiogoniometer coil and a-variable resistance connected between the midpoint of the ra diogoniometcr coil and the ground. I

GJ'In a system of the classjdescribed, a radiogoniometer coil having acondenser therein, a plurality of vacuum tubes associated withoppositeplates of said condenser, a plurality of inductances associated withsaid condenser, and means for variably coupling said inductances withthe plate circuit of one of said vacuum tubes. 2 7.,Ina directionalaerial system, a loop antenna, a variable condenser in series therewith,a connection between the electrical midpoint of said loop and ground, aresistance in said connection, a pair of thermionic tubes each havingcathode anode and control I antenna,a pair of inductancesand a variablecondenser in series with saidloop, a connectionbetween the electricalmidpoint of said loop and ground, a resistance in said'connection, apair-of thermionic tubes each having cathode, anode and vcontrolelectrodes, grounded heating means for said cathodes,

a direct connection between eachiterminal of said condenser and thecontrol electrode of one of saiditubes, and an inductance in the anodecircuit'of one-of said tubes variably coupled to said first namedinductances.

ETTORE BELLTNI.

